A handful of moderate Republican senators are now expected to cast the key votes on the fate of this controversial proposal that promises to have a lasting effect on Maine.

Republicans say their caucus stands solidly in support of Gov. LePage. They argue that opting out of the Medicaid expansion allowed by the federal Affordable Care Act will prevent Maine from making a structural change in the program that the state cannot afford.

“The question of Medicaid expansion is not very popular within the Republican caucus,” said House Republican Leader Kenneth Fredette of Newport. “At the end of the day, there are not enough of those Republicans to override the veto. As a state we’ve just jumped into this game too quickly.”

Democrats and liberal advocacy groups, such as the Maine People’s Alliance, that support Medicaid expansion say they are confident enough Republicans will break with the governor and override his veto.

“We’re pushing Republicans to do the right thing and provide health care for 70,000 Mainers,” said Speaker of the House Mark Eves, D-North Berwick, on Tuesday afternoon. “I know that they understand what is at stake here.”

If the Legislature overrides LePage’s veto — which hasn’t happened on any of the 18 bills the governor has vetoed so far this year — tens of thousands of low-income Mainers will gain access to health coverage that they otherwise couldn’t afford.

But an override would require more Republican votes in both the House and Senate than LD 1066 — the latest bill for Medicaid expansion — garnered for its approval last week. It passed in the House 97-51 and in the Senate 23-12.

Those tallies fall four votes and one vote short of the two-thirds majority needed to override a veto, respectively.

Lobbyists who are paid to win votes in favor of the expansion said they’re hopeful. Ben Chin, political engagement director for the Maine People’s Alliance, said his organization and others are singularly focused on convincing Republicans to buck LePage.

“If every Republican who has voted for Medicaid expansion once votes for an override, we’re in good shape,” said Chin. “There is a huge set of moderate Republicans we’re hopeful around. I still feel confident on the House side because we see a lot of people coming back and forth. It’s a pretty good sign that there’s some play.”

In the Senate, three Republicans voted for the expansion last week: Sen. Patrick Flood, R-Winthrop; Sen. Roger Katz, R-Augusta; and Sen. Tom Saviello, R-Wilton. Flood and Katz told the Bangor Daily News unequivocally Tuesday they will vote to override the veto.

“I believe it’s a close question,” said Katz. “On balance, I think it makes sense for Maine and I also know that 11 or 12 other Republican governors thought it was the best move for their states.”

Katz successfully offered an amendment to allow Maine to leave the program after the three years in which the federal government pays 100 percent of the expansion costs, to try and make Medicaid expansion more palatable to Republicans.

Chin described at least three other Republican senators as “on the fence.” One of them is Sen. Brian Langley, R-Ellsworth, one of five Republican senators who last week broke party ranks to support a biennial budget opposed by LePage.

“In general I think there is a greater portion of the Republican caucus on the Senate side that is open to hearing what is good for the state,” said Chin.

Langley said Tuesday that he is being targeted by more than one group, some of which have posted his telephone number online. He said his phone has been ringing steadily, but refused to say how he will vote on a veto override. He did say that he has serious concerns about the ramifications of accepting the federal deal.

“I’ve done my homework and I’ve had a lot of conversations with people,” he said. “For me, this is about long-term sustainability. Between Medicaid expansion and the Affordable Care Act, I’m worried that our medical system as a whole will just implode.”

Because LD 1066 originated in the House, that chamber will vote first on Monday’s veto. Eves said Tuesday a veto override vote could come anytime between Tuesday evening and the end of the week. By law, the Legislature has seven days to act on a gubernatorial veto.

LD 1066 would sign Maine up for a federally funded Medicaid expansion offered under the federal Affordable Care Act. It would provide coverage for some 50,000 adults without children who earn up to 133 percent of the federal poverty level, which is $20,628 for a two-person household. It would also prevent about 25,000 parents and childless adults from losing their Medicaid coverage in January 2014. Nearly 10 percent of Mainers are currently without health insurance.

While the federal government promises to pay 100 percent of expansion costs for the first three years before gradually reducing its support to 90 percent by 2020 — which Democrats contend is too good a deal to pass up — Republicans say accepting the deal would be a continuation of years of what they call “welfare expansion” that consumes far too much of the state budget.

The Cover Maine Now coalition, which includes 85 organizations that support Medicaid expansion, launched an intensified lobbying effort Tuesday. The group plans a rally Wednesday at the State House, the posting of signs at businesses, writing letters to newspapers and a phone campaign targeting legislators at their homes.

In past House floor speeches, Fredette said he didn’t necessarily oppose Medicaid expansion, but he said Tuesday that his opposition has solidified.

“People need to look at what has happened in the past 10 years,” he said. “Medicaid is out of control. We’ve had supplemental budget after supplemental budget because of our unpaid bills. At this point in time I am against it.”